Conventionally, a current sensor has been used to detect a charging/discharging current of a battery of a car and to detect a current flowing between a battery and an inverter of a hybrid car or an electric car. As described in JP 2012-47563A, the current sensor has a structure in which a conductor such as a bus bar is inserted through an annular magnetic core and a magneto-electric conversion element such as a Hall element is disposed in a gap formed by cutting out a portion of the circumference of the magnetic core. The magneto-electric conversion element converts a magnetic flux generated by current flowing through the conductor into voltage signals, and thus the current flowing through the conductor is detected.
Incidentally, in such a current sensor, it is necessary to insert the conductor in which a current is to be detected through the magnetic core accommodated in a case through an opening portion of the case. However, it is often difficult to insert the bus bar through the opening portion of the case, as the bus bar has a complicated shape that sometimes has a width dimension that is larger than that of the opening portion or is sometimes provided with a large number of bent portions.
Therefore, conventionally, as described in JP 2012-47563A as well, the current sensor for detecting a current flowing through the bus bar has a structure in which a detection target portion of the bus bar to be inserted through the magnetic core is separately formed and projects from the case, and both ends of the detection target portion of the bus bar that project from the case are connected to another bus bar.
However, in the structure as described in JP 2012-47563A, heat is generated due to contact resistance between the bus bar that projects from the case and another bus bar that is connected thereto in the portions in which the bus bars are connected to each other. Then, there is a risk that the heat generation due to the contact resistance between the bus bars affects the magneto-electric conversion element, and thus the detection accuracy is lowered. Moreover, the contact resistance depends on the tightening torque of a bolt for fixing the bus bars to each other, and therefore, there is a problem in that it is necessary to accurately control the tightening torque of the bolt and thus production man-hours increase.